EP0185267A2 - Injectable plastisol composition and its use in sound isolation - Google Patents

Abstract

• a) 32 bis 72 Gew.% an Vinylchloridhomopolymeren und/oder VinylchloridNinylacetatcopolymeren,
• b) 28 bis 60 Gew.% einer Weichmachermischung aus
  • b1) 0 bis 30 Gew.% (bezogen auf das Vinylchloridhomo-und/oder copolymer) an üblichen Weichmachern für Vinylchloridpolymere, die mit dem ggf. vorhandenen Polymer c) nicht verträglich sein dürfen, und
  • b2) mit dem Polymer c) verträglichen organischen Weichmachern, die mit dem Polymer a) im wesentlichen unverträglich sind, sowie
• c) für den Fall, daß b2) ₂:
  
  , mindestens 15 Gew.% (bezogen auf den Weichmacher b2) an Methylmethacrylathomopolymeren oder -copolymeren mit copolymersierbaren Monomeren, deren Glastemperatur T_g ≥ 65°C beträgt, enthält.

Plastisols, which are particularly suitable as a sprayable plastisol composition, contain, in addition to 2 to 40% by weight (based on the plastisol), fillers and, if appropriate, customary auxiliaries as polymers and plasticizers, a mixture of

• a) 32 to 72% by weight of vinyl chloride homopolymers and / or vinyl chloride-vinyl acetate copolymers,
• b) 28 to 60% by weight of a plasticizer mixture
  • b1) 0 to 30% by weight (based on the vinyl chloride homo- and / or copolymer) of customary plasticizers for vinyl chloride polymers which must not be compatible with the polymer c) which may be present, and
  • b2) organic plasticizers compatible with the polymer c), which are essentially incompatible with the polymer a), and
• c) in the event that b2) ₂ :
  
  contains at least 15% by weight (based on plasticizer b2) of methyl methacrylate homopolymers or copolymers with copolymerizable monomers, the glass transition temperature of which is T _g 65 65 ° C.

Description

As is known, the maximum of the acoustic damping of organic polymers is somewhat above their glass transition temperature T, the maximum also being dependent on the respective frequency. In practice, one tries to make the most of this noise reduction effect for noise abatement. The respective acoustic loss factor d of a mass results from its internal loss factor d ₂ and its elastic modulus E2, an expression for the bending stiffness of the mass. The maximum attenuation in the human hearing range should be between 20 and 20,000 Hz at the usual usage or environmental temperature of around 20 to 30 ° C.

The glass transition temperature of many polymers, e.g. of methyl methacrylate / butyl methacrylate or vinyl chloride / vinyl acetate copolymers is in this range because the comonomers lead to an internal softening of the polymers. However, these soft but non-liquid polymers cannot be sprayed unless they are brought into a liquid phase. This is usually done by dispersing in water or by dissolving in a sufficient amount (> 30%) of a suitable solvent. However, the water or the solvent must be removed again after the application of the mass with considerable expenditure of time and energy. Aqueous systems cause corrosion problems, systems based on organic solvents lead to increased costs and considerable environmental problems, and both also only allow relatively thin layers.

Another possibility is to disperse a polymer powder in an organic plasticizer, which does not dissolve the powder at room temperature, but leads to gelation when heated. Such systems are known as plastisols, and they can be produced in particular from polyvinyl chloride or from acrylic polymers ( ^{cf. rgl. DE} - ^PS _{24 54 235} and 25 29 732). The viscosity of a sprayable plastisol must be below 50 dPa.s. When processing in a modern, air-free spraying device, the viscosity must even be <30 dPa.s, measured with the rotary viscometer (Rheomat 15).

Acoustics and noise abatement are primarily concerned with the human hearing range, i.e. the frequencies between 20 and 20,000 Hz, with 200 Hz generally being selected as the standard measuring frequency. The method for determining the attenuation at these frequencies is specified in DIN 53440, according to which the attenuation maximum can also be determined depending on the temperature.

It is known from the literature (F. Linhardt, Kunststoffe 53, 18-21 (1963)) that for the polyvinyl chloride / dioctyl phthalate system the damping maximum for 1 _H z is 20 ° C. at a ratio of 67:33 and at a ratio of 60: 40 drops to 0 ° C. However, the viscosity of this latter plastisol is still 100 dPa.s (see company publication "Plasticizers in the plastics industry" from Chemische Werke Hüls _AG , November 1976, page 9). It should be noted that the viscosity of plastisols is largely dependent on the respective shear rate. Since spraying always takes place at a high shear rate (this applies even more to air-free spraying), this always means the viscosity at more than 350 rpm. In addition, the viscosity is strongly dependent on the respective polyvinyl chloride and soft material. _ch ertype dependent. Plasticizers that give lower viscosities than dioctyl phthalate also have a more plasticizing effect (eg dibutyl phthalate or dioctyl adipate), so that the maximum damping is at even lower temperatures than when using dioctyl phthalate with the same mixing ratio.

Viscosity lowerers such as emulsifiers have little influence on polyvinyl chloride types of low viscosity, but can help to further reduce the damping maximum. In addition, a polyvinyl chloride plastisol that meets the requirements in practice must contain other components such as thixotropic agents, pigments, heat stabilizers, possibly adhesion promoters and in any case fillers which increase the acoustic damping by improving the bending stiffness, but at the same time also lead to an increase in viscosity. In this way it is therefore not possible to produce polyvinyl chloride plastisol which at the same time has the required low viscosity and a glass transition temperature in the range from approximately 20 to 30 ° C.

The situation is different with the acrylic plastisols mentioned above. In polymethyl methacrylate and its relatively hard copolymer whose _Tg approximately 30 ° higher than is in the polyvinyl chloride, can accordingly be found, to decrease T to the operating temperature more plasticizers used, so that the optimum damping at a ratio of _P oly- mer: plasticizer of 1: 1 1 is reached. Accordingly, an acoustically good damping compound with good sprayability can be produced from this. With an approximately constant ratio of 1: 1 to achieve the maximum damping at ambient temperature, a plasticizer content of 35% by weight and a polymer content of also 35% by weight with the addition of 30% by weight of auxiliaries can still be used Make sprayable plastisol. However, polymethyl methacrylate and its copolymers are about 3 to 4 times more expensive than polyvinyl chloride. The plastic gels obtained from these plastisols also have significantly lower tear and abrasion resistance and only relatively few plasticizers can be used.

The invention has for its object a polyvinyl chloride plastisol, the maximum attenuation in the gelled state of about 20 to 30 ° C, with the addition of at most 10 wt.% Of dilution to a viscosity of less than 50 dPa.s and thus in a sprayable form bring to. Such a plastisol or organosol could, for example, be used for soundproofing machine housings or car bodies and would offer very considerable advantages in terms of application technology. For example, one could spray out the cavities of motor vehicle doors with such a plastisol and thus achieve effective sound insulation in the simplest way. It would also be possible to design the underbody protection of motor vehicles to be sound-absorbing. The currently Underbody protection agents used in practice are acoustically effective because, due to the high plasticizer content, their damping maximum is at far too low temperatures.

• a) 32 bis 72 Gew.% an Vinylchloridhomopolymeren und/oder Vinylchlorid/Vinylacetatcopolymeren,
• b) 28 bis 60 Gew.% eines Weichmachers bzw. einer Weichmachermischung aus
  • b1) 0 bis 30 Gew.% (bezogen auf das Vinylchloridhomo-und/oder copolymer) an üblichen Weichmachern für Vinylchloridpolymere, die mit dem ggf. vorhandenen Polymer c) nicht verträglich sein dürfen, und
  • b2) mit dem Polymer c) verträglichen organischen Weicnmachern, die mit dem Polymer a) im wesentlichen unverträglich sind, sowie
• c) für den Fall, daß b2) >
  
  , Gew.% , mindestens 15 Gew.% (bezogen auf den Weichmacher b2) an Methylmethacrylathomopolymeren oder -copolymeren mit copolymersierbaren Monomeren, deren Glastemperatur Tg > 65⁰C beträgt,

enthält.It has surprisingly been found that the above object can be achieved by using a selected plasticizer in very specific proportions or two different plasticizers and, if necessary, using an additional polymer in order to prevent the second plasticizer from exuding. The invention accordingly relates to a sprayable plastisol composition with a viscosity of less than 50 dPa.s at 350 rpm based on powders of organic polymers and plasticizers and 2 to 40% by weight (based on the composition) of inert fillers and, if appropriate, customary auxiliaries and, if appropriate, up to 10% by weight of inert diluents, characterized in that they are a mixture of polymers and plasticizers

• a) 32 to 72% by weight of vinyl chloride homopolymers and / or vinyl chloride / vinyl acetate copolymers,
• b) 28 to 60% by weight of a plasticizer or a plasticizer mixture
  • b1) 0 to 30% by weight (based on the vinyl chloride homo- and / or copolymer) of customary plasticizers for vinyl chloride polymers which must not be compatible with the polymer c) which may be present, and
  • b2) organic plasticizers compatible with the polymer c), which are essentially incompatible with the polymer a), and
• c) in the event that b2)>
  
  , Wt.%, At least 15 wt.% (Relative to the plasticizer b2) of Methylmethacrylathomopolymeren or copolymers with copolymerizable monomers whose glass transition temperature Tg> 65 ⁰ C,

contains.

ist. Sobald b2 diesen Wert überschreitet, wird erfindungsgemäß ein Methylmethacrylathomopolymer oder -copolymer zugesetzt, welches mit dem Weichmacher b2 verträglich ist und diesen beim Gelieren aufnimmt und dadurch dessen Ausschwitzen verhindert.A prerequisite for the success of the invention is that the plasticizer bl only gels with the polymer a and the plasticizer b2 only with the polymer c (ie is compatible), so that the glass transition temperature T _{g of} the plastic gel is essentially due to the combination polymer a / plasticizer b1 is determined, while plasticizer b2 ensures the required low viscosity of the system before gelling. Surprisingly, it was also found that there is a very narrow range in which a plastisol with the required low viscosity is obtained from polymer a and plasticizers b1 and b2, which, after gelling, contains a plastigel with a glass transition temperature> 20 ° C. forms, from which the plasticizer b2 does not yet exude. This range is defined by the fact that with the percentage composition b2> given above

is. Once b2 this value exceeds, according to the invention a methyl methacrylate homopolymer or copolymer is added which is compatible with the plasticizer b2 and absorbs it during gelling and thereby prevents it from exuding.

A polyvinyl chloride powder or a vinyl chloride / vinyl acetate copolymer powder is used as polymer a, the latter preferably having a vinyl acetate content of up to 20% by weight. Suitable polymer powders can be produced by means of emulsion, suspension or precipitation polymerization. The water can be removed from the dispersion by spraying, rolling, evacuating or evaporating.

It is advantageous to use a mixture of two or more types instead of a copolymer, which deliver different T values with the respective plasticizer, so that one does not obtain a damping maximum at a specific temperature, but rather several maxima lying next to one another that there is a maximum band.

All conventional PVC plasticizers known per se can be used as plasticizer b1. If polymer c is present, only those plasticizers are suitable which are incompatible with polymer c and accordingly do not gel. The C ₇ to C ₁₀ alkyl phthalates, in particular dioctyl phthalate and dinonyl phthalate, are to be mentioned primarily for this purpose. Adipates, sebazates and phosphates such as dioctyl adipate, dioctyl sebazate and dibenzyl sebazate are also suitable.

Plasticizer b2 must be selected very carefully, since there are only a few plasticizers that do not contribute to the gelation of polyvinyl chloride or its copolymers. Dibenzyltoluene has proven to be particularly suitable. Dodecylbenzylbenzene, terphenyl, certain aromatic oils and diphenyl ether are also suitable.

Polymethyl methacrylate or its copolymers with a Tg> 65 ° C. are used as polymer c. A copolymer of methyl methacrylate and up to 20% by weight of butyl methacrylate is particularly preferred. So-called core / shell types are also suitable, i.e. Acrylic polymer powder, the core and the shell of which are made of different acrylic polymers. Suitable examples can be found in DE-AS 27 22 752.

In addition to the main components mentioned above, there are also. the most diverse additives into consideration, so that in this respect the entire plastisol technology can be adopted for the systems according to the invention. The plastisols according to the invention can also be organosols containing up to 10% by weight of organic diluents. Suitable solvents are in particular higher-boiling isoparaffins (e.g. ISOPAR®), the compositions with good. Deliver stability.

Since the acoustic effectiveness of a coating depends, among other things, on the layer thickness, it can often be advantageous to add a blowing agent such as azodicarbonamide to the plastisol composition. The same effect can also be achieved with the help of fillers in the form of hollow spheres. Such compositions with a particularly low density are particularly suitable for use in places where other mechanical properties such as, for example, high abrasion resistance do not play a role, in particular for double-walled housings for machines, for example dishwashers, or for the doors of motor vehicles. In many applications, the addition of adhesion promoters is required. These include in particular the various polyaminoamides, which also help to lower the viscosity, as well as peroxides together with mono-, di- and trimethacrylates, epoxy resins with their hot hardeners (e.g. dicyandiamide), phenolic resins, blocked and unblocked diisocyanates, which also ensure this as crosslinkers can, that the damping curve of the plastic gels does not drop so much after higher temperatures. Crosslinking of the polyvinyl chloride with the polymethyl methacrylate is also conceivable if the polymethyl methacrylate contains groups which react with chlorine, for example epoxy or amine groups. For the plastisols, emulsifiers which regulate or reduce the paste viscosity, for example polyethylene oxide derivatives, can be useful. however, they must not lower the T. Thermal stabilizers are required for use at higher temperatures. Epoxy plasticizers and heavy metal compounds, in particular those of lead, cadmium, tin and zinc, are known for this.

Finally, fillers which may also be coated may be mentioned as essential additives. Usually find chalk, heavy spar, dolomite, silicates, vermiculite, talc, mica, carbon, coke, graphite, or _e-M-metal oxides such as aluminum oxide, calcium oxide, zinc oxide, titanium dioxide or silicon dioxide used. Organic or inorganic hollow spheres have already been mentioned above as fillers which are also suitable.

The plastisol compositions according to the invention are gelled at temperatures between 80 and 230 ° C. after the composition has been sprayed onto the substrate to be treated, generally a sheet metal surface. _I nquestion coming applications include household and office appliances such as washing machines and dishwashers, sinks and basins, _S chreib- and calculating machines, and motor vehicles, in particular their roofs (inside), underbody, doors, trunk and engine compartment hoods, side walls etc.

The following examples are intended to explain the invention in more detail. Unless otherwise stated, all plastisols were gelled at 140 ° C. for 20 minutes. The damping values were determined according to DIN 53445 or DIN 53440. The plastisols were applied to the measuring strips using a thinly applied adhesive primer.

The quantities in the following table are in parts by weight. Where necessary, the proportions for components a, b1 and b2 are given in% (in each case based on the combination of a with b1 and b2) in brackets.

Experiments I to VI represent comparative experiments, while Examples 1 to 8 illustrate the invention.

Wie die vorstehenden Ergebnisse zeigen, weisen Plastisole außerhalb des beanspruchten Bereiches für eine Spritzverarbeitung zum Teil eine zu hohe Viskosität auf. Darüber hinaus liefern sie Plastigele mit ungenügender Weichmacherverträglichkeit und/oder ein Dämpfungsmaximum bei einer zu niedrigen Temperatur, so daß die akustische Dämpfung und damit die Kennzahl bei Normaltemperatur von 20 bis 30°C unbefriedigend ist. Angestrebt werden eine Kennzahl < 55 und ein E-Modul > 2 · 10⁸ Pa.table

As the above results show, plastisols outside the claimed range are in some cases too viscous for spray processing. In addition, they supply plastic gels with insufficient compatibility with plasticizers and / or a damping maximum at a temperature that is too low, so that the acoustic damping and thus the characteristic number at normal temperature of 20 to 30 ° C. are unsatisfactory. The aim is to achieve a key figure <55 and an elastic modulus> 2 · 10 ⁸ Pa.

The results also show that plastisols based on PVC or PVC / VA, which are suitable as plastisol compositions, can be obtained in a narrow range even without the addition of polymethyl methacrylate. It is particularly surprising that despite the high proportion of plasticizer b2, which does not gel polyvinyl chloride, sufficient plasticizer compatibility (no exudation of the plasticizer) is nevertheless obtained. According to the information in the literature (Hüls, a.a.0.), The tolerance limit is at much lower amounts b2.

Claims (1)

1. Sprayable plastisol composition with a viscosity of less than 50 dPa.s at 350 rpm based on powders of organic polymers and plasticizers and 2 to 40% by weight (based on the composition) of inert fillers and, if appropriate, customary auxiliaries and, if appropriate up to 10% by weight of inert diluents, characterized in that they are a mixture of polymers and plasticizers a) 32 to 72% by weight of vinyl chloride homopolymers and / or vinyl chloride / vinyl acetate copolymers, b) 28 to 60% by weight of a plasticizer or a plasticizer mixture b1) 0 to 30% by weight (based on the vinyl chloride homo- and / or copolymer) of customary plasticizers for vinyl chloride polymers which must not be compatible with the polymer c) which may be present, and b2) organic plasticizers compatible with the polymer c), which are essentially incompatible with the polymer a), and c) in the event that b2) _>

% By weight, at least 15% by weight (based on plasticizer b2) of methyl methacrylate homopolymers or copolymers with copoly mersible monomers whose glass transition temperature T is> 65 ° C,
contains. Plastisol composition according to claim 1, characterized in that the vinyl chloride / vinyl acetate copolymer has a vinyl acetate content of up to 20% by weight. Plastisol composition according to one of claims 1 or 2, characterized in that it contains C ₇ to C ₁₀ alkyl phthalates as plasticizers b1). Plastisol composition according to one of claims 1 to 3, characterized in that it contains dibenzyltoluene as plasticizer b2). Plastisol composition according to one of claims 1 to 4, characterized in that it contains, as methyl methacrylate copolymer, a copolymer of methyl methacrylate and up to 20% by weight of butyl methacrylate. Plastisol composition according to one of claims 1 to 5, characterized in that it contains one or more chemically crosslinking substances. Plastisol composition according to one of claims 1 to 6, characterized in that it contains a blowing agent, preferably azodicarbonamide. Use of the composition according to claims 1 to 7 for sound absorption of sound-emitting metal surfaces by spraying the composition onto the surfaces and subsequent heat curing.